Feedthrough assemblies are employed in implantable medical devices (IMDs) for a variety of uses (e.g., to provide a pathway for one or more electrical leads through an IMD's container or through the casing of an electrochemical cell, such as a battery or capacitor). For example, feedthrough assemblies are commonly employed in IMD capacitors to guide an electrical lead through a capacitor's casing and electrically insulate the lead therefrom. Such a feedthrough assembly may comprise a metal ferrule (e.g., titanium) that is fixedly coupled (e.g., welded) to the capacitor's casing and an insulative structure disposed within the ferrule. The insulative structure secures and insulates the lead within the ferrule. The insulative structure also forms a hermetic seal within the ferrule, which may, in the case of a wet capacitor, help retain electrolytic fluids.
One known type of insulative structure comprises a compression seal stack including a polymeric compression ring (e.g., a silicon based material, nitrile, natural rubber, etc.) having an aperture therethrough for receiving the lead. The compression ring is threaded over the lead and positioned within a ferrule between two rigid insulating members (e.g., chromium doped alumina). The compression seal stack is then compressed causing the compression ring to expand radially between the insulating members and sealingly engage the outer surface of the terminal lead and the inner surface of the ferrule. A hermetic seal is thus formed within the ferrule. The seal stack may then be secured in its compressed state by crimping an end portion of the ferrule in the manner described below.
A compression and crimping apparatus may be utilized to compress the compression seal stack and crimp the ferrule of a feedthrough assembly. One such apparatus comprises two compression jaws that travel along a longitudinal track in a clamp-like manner. Both of the compression jaws include an opening (e.g., a slot) therein for receiving a segment of the lead, and each is configured to engage an opposite end of the ferrule. The jaw engaging the ferrule opposite the crimping portion may simply comprise a generally flat surface that acts as a support during crimping. In contrast, the compression jaw engaging the crimpable end portion of the ferrule comprises a well having an inclined surface and an island protruding upward from a central portion of the well. When the jaws are moved toward one another, the island forces the second insulating member further into the ferrule thereby compressing the compression ring and forming a hermetic seal within the ferrule. Additionally, the inclined surface of the well contacts and crimps the end portion of the ferrule to secure the seal stack in its compressed state and thus maintain the hermetic seal within the ferrule.
Compression and crimping devices of the type described above have certain limitations. For example, such devices do not permit the independent articulation of the crimping component (i.e., the inclined surface of the well) and the seal-forming component (i.e., the island). Thus, known devices are unable to adjust the seal-forming load independent of the crimping-load to, for example, accommodate for dimensional variations in the components of the compression seal stack. This, in turn, restricts the tolerance to which the components of the compression seal stack may be manufactured and decreases product yield. In addition, the crimping component in known devices may not be individually replaced with wear caused by repetitive crimping or interchanged with other components adapted to crimp different ferrule types.
Considering the above, it should be appreciated that it would be desirable to provide a compression and crimping apparatus that permits the independent articulation of the crimping component and the seal-forming component. It should also be appreciated that it would desirable for such an apparatus to permit the replacement and customization of the crimping component. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.